This invention relates to electron devices comprising a thin-film electron emitter formed with a semiconductor film, particularly but not exclusively of a silicon material such as hydrogenated amorphous and/or microcrystalline SiC.sub.x or SiN.sub.y or SiO.sub.x N.sub.y or Si. Preferably a thin-film array of such electron emitters are formed side-by-side in the semiconductor film. The electron device may be, for example, a flat panel display.
The paper "Experiments of highly emissive metal-oxide-semiconductor electron tunnelling cathode" by Yokoo et al in J. Vac. Sci. Technol. B 14(3), May/June 1996 pp 2096-2099 discloses a thin-film electron emitter comprising an insulating oxide film through which electrons tunnel from an n-type substrate into a gate which provides an emission area from which the electrons are emitted. The gate comprises an aluminium gate electrode on a n-type doped silicon semiconductor film on a 20-30 nm thick non-doped silicon semiconductor film on the oxide insulating film. The thickness of the 20-30 nm thick non-doped silicon semiconductor film is such as to support a depletion layer which establishes an accelerating field for the electrons from the oxide film to the emission area with lower scattering probability than in the oxide film, so increasing the emission efficiency. The whole contents of this J. Vac. Sci. Technol. paper are hereby incorporated herein as reference material.
The paper "Amorphous-Silicon-on-Glass Field Emitter Arrays" by Gamo et al in IEEE Electron Device Letters Vol 17, No 6, June 1996 pp 261-263 describes a thin-film array of electron emitters formed side-by-side in a semiconductor film, an electron source at the back face of the semiconductor film for supplying electrons to the semiconductor film, and an array of emission areas at the front of the semiconductor film from which electrons are emitted in operation of the device. The semiconductor film of 1 .mu.m thick amorphous silicon is sputter deposited on a bottom contact and divided up into separate conical emitters at windows in an insulating film on the device substrate. This insulating film carries an apertured gate, which is thereby insulated from the underlying bottom contact. The tip of the cone forms the emission area of the emitter, and the emission characteristics are dependent on the quality of the tip, which is not easy to control during manufacture. These emitters require a high gate voltage for operation. The whole contents of this IEEE Electron Device Letters paper are hereby incorporated herein as reference material.
The paper "Nitrogen containing Hydrogenated amorphous Carbon for Thin-film field emission Cathodes" by Amaratunga and Silva, published in Applied Physics Letters Vol.68 No.18, Apr. 29, 1996, pages 2529 to 2531 describes a thin-film electron emitter formed in a semiconductor film (of 0.3 .mu.m thick amorphous carbon). The emitter comprises a highly doped n-type silicon substrate forming the cathode electrode at a back major surface of the semiconductor film, and an oppositely located emission area at the front major surface of the semiconductor film from which electrons are emitted in operation of the device. Uniform emission of electrons over the entire front major surface of the carbon film was observed at low current densities (below 7.times.10.sup.-2 mA.cm.sup.-2). At higher current densities preferential emission from uncontrolled spots was observed. It is suggested that, by adopting a triode configuration, the emitter may be suitable for switching a display element. The fabrication of a thin film array of emitters is not described in any configuration. The whole contents of the Applied Physics Letters paper are hereby incorporated herein as reference material.